Optimization of Deformable-Adhesive Application on the Chip-Apply Process

Abstract:

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A study on the impact of batch-to-batch variability of a commercial wet adhesive on its plastic deformation behaviour is here presented. In the chip-apply process, a controlled and stable plastic deformation under thermal-mechanical compression is expected after the first of a two-step curing, named pre-cure. Wet adhesive batches rheological, mechanical and chemical characteristics are available but no information on deformation behaviour is provided. Different pre-curing recipes and oven atmospheres were tested and the plastic deformation was induced by applying pre-defined thermo-compression parameters. Results indicate that shorter pre-cure cycles at higher temperature, under air atmosphere, reduce batch-to-batch deformation variability. DSC curves support these findings. A correlation between deformation level and rheological properties could also be observed, which can be very useful in the triage of adhesive batches for specific process parameters
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Abstract: UV curing adhesives have been introduced for bonding various materials at a room
temperature. It has the advantage of putting minimum thermal load on the system; however, it is not
suitable for precision bonding of micro systems such as micro optical devices because of its high
viscosity and poor control of the UV light source. In the present work, a laser-curing bonding
process of micro optical devices with a low-viscosity UV polymer adhesive has been developed. A
focused Nd:YVO4 laser beam with a spot size of 30 µm with a laser power of 100 ~ 700 mW is
used for curing a UV adhesive locally. A thin bonding layer with a thickness of a few hundred
nanometers without any thermal effects can be obtained for precision laser bonding for optical
fibers. Experimental results are provided and the process characteristics have been discussed.
Moreover, potential applications in the field of micro optical systems are introduced as well.

Abstract: Modified neoprene adhesive dedicated to bonding UHMWPE and 45# steel was prepared. Thermal analysis with TG-DTG curve was determined and its thermal decomposition kinetics was studied. The result show that the thermal degradation process of CR/MMA/CPE/MgO adhesive is a three-step reaction and the its thermal degradation starting temperature is 200°C and complete decomposition temperature is 570°C. The first mass loss stage is 0.6 order chemical reaction and its average activation energy E is 19.21kJ/mol and pre-exponential factor A is 3.68×102. The second mass loss stage is 3 order chemical reaction and its average activation energy E is 82.14kJ/mol and its pre-exponential factor A is 1.52×108. The third mass loss stage is 3 order chemical reaction and its average activation energy E is 55.07kJ/mol and pre-exponential factor A is 1.33×105.

Abstract: This paper presents a method of low temperature wafer level adhesive bonding using non-photosensitive bisbenzocyclobutene (BCB) from Dow Co for resonant pressure sensor package. The bonding process is performed at the temperature below 250oC, with the pressure on the wafer 2-3 Bar in vacuum in a wafer bonding system. According to the bonding process, pre-bake time, pumping time, pressure placed on the sensor and the thickness of cross-linked layer are the most important factors. Experiments show that more than 95% of the area is successfully bonded, the hermeticity maintains well after thermal shock and long term tests, and the tensile strength of the fabricated bonds is up to 40MPa. The bonding technique was successfully tested in the fabrication process of resonant pressure sensor, and the results show that this bonding technique is a viable MEMS encapsulation technology for hermetically cavity sealing.

Abstract: Epoxy adhesive used in electronic packaging could normally be cured by ultraviolet light, heat at high temperature or dual cured by both processes. Differential scanning calorimetry (DSC) has been used to identify and analyze the occurred reaction during the curing process. The structural modification of epoxy during curing could be examined by measuring its thermal properties, and the change in molecular structure of epoxy could be observed by a relative small area of DSC peak. This provided the heat amount required for complete cure. It is found that the DSC peak area after heat cure at 90 °C increased linearly as a function of heating time while that at 120 °C decreased exponentially. For UV cure, it indicated that the curing mechanism was strongly depend on the energy from UV light. For dual cure at 90 °C, the heat curing time could be reduced from single curing process of 50 minutes to 6 minutes, while the heating time for dual cure at 120 °C could be reduced from 4 minutes to 2 minutes.

Abstract: Pultrusion is a composite manufacturing technique for processing continuous composite profiles with a constant cross section. In such system, energy and mass balances are used to model the thermal and kinetic behavior of the material during processing. This work aims to compare the results obtained in the recent literature, regarding thermal optimization of pultrusion. In the present analysis, an alternative thermal configuration has been suggested, with the objective of maximizing the mean degree of cure. A general-purpose FE software, ANSYS-CFX®, has been used to perform a three-dimensional (3D) conductive heat transfer analysis. Several case studies were conducted where the degree of cure was analyzed for varying heating scenarios. Results have shown that it is possible to get a higher cure in less process time if the die is isolated from the environment.